1. Field of the Invention
This invention resides in the field of biochemical laboratory equipment, and specifically equipment for slab gel electrophoresis.
2. Description of the Prior Art
Electrophoresis in slab-shaped gels is a common analytical technique in biotechnical laboratories in view of the many beneficial features that slab gels offer to the analytical chemist or biochemist. A slab gel can be divided, for example, into several lanes and a separate analysis can be performed in each lane while all are performed under the same conditions. Also, slab gels are easily removed from their enclosures for staining to make the solute bands visible. Further, the flat, two-dimensional configuration of a slab gel allows the gel to be easily scanned for identification and quantification of the contents of each band by automated instrumentation.
Slab gels are commonly held in cassettes that essentially consist of a pair parallel plates separated by a gap that defines the thickness of the gel. The gel is cast in the cassette by filling the gap with a solution of the gel-forming monomer or prepolymer and allowing the solution to polymerize. Once the gel is cast, samples are loaded along the top edge of the gel and electrophoresis is performed with the top and bottom edges of the gel in contact with electrodes through buffer solutions. Examples of cassettes of this type are those described in Leka, U.S. Pat. No. 5,411,657, May 2, 1995, and Van Atta, U.S. Pat. No. 6,093,301, Jul. 25, 2000.
Casting the gel in the manner described above requires temporary sealing of the bottom edge of the gel space in such a manner that removal of the seal leaves the gel with a cleanly defined bottom edge. A commonly used seal is a strip of flexible adhesive-backed tape. While the tape can be removed without tearing the gel, a difficulty with this method is that the two plates are typically welded together along their side edges leaving a weld line where the plates meet, and the weld line, even when covered by the tape, is a common site for leakage. To avoid this, cassettes have been designed with a closed bottom and a slot in one of the plates near and parallel to the bottom. The resulting gel has a “foot” along its lower edge that protrudes laterally through the slot. The foot deviates from the planarity of the remainder of the gel, however, which lowers clarity and accuracy during detection of the bands in the gel.